I've been speaking with a number of people who had this problem (and I did as well). The gist of it is, when you try to use the built-in documentation browser in the Xcode organizer, you are prompted to enter your password. (Which you can't actually do)
The solution was non-obvious to me, but here it is:
- Open Preferences > Downloads
- Choose the Documentation Tab
- Click "Install" for the documentation sets you wish to use
Once they're done installing, you'll be able to access the docs normally.